Today the popular on-demand grocery delivery service Instacart announced that it is bringing its service to two new cities: Oakland and Berkely. The two cities join its other active locations, all of which fall inside of the Bay Area.

Instacart appears to be succeeding where other firms have failed; it appears to have made grocery delivery economically viable. The service earns its keep by charging a fee for delivery – it costs more to get your goods sooner, and you tip delivery people on top of that – and by charging small markup on items sold.